Brooks Harris replied to Paul Eggert:
PS. I see that the draft sometimes says "leap second" and sometimes "leap-second". I assume that follows some editorial rule that I don't remember. The above text might need hyphenization to fix that.
ITU-R Recommendation 460, the specification of the leap-second, spells "leap-second" with the hyphen. I feel that's the "proper" spelling because it comes from the ITU-R document.
Most usage in American English, outside of standards documents, trends toward “leap second,“ just as it trends toward “leap year” rather than “leap-year.” The general rule (again in American English) is to spell a compound like this as two words when using it as an ordinary noun, but hyphenate it when using it as an attributive noun. So you would have “leap-second rules” that determine the application of “leap seconds.” The attributive-noun convention (see what I did there?) is helpful to disambiguate phrases that contain long strings of nouns. See https://en.wikipedia.org/wiki/English_compound for more. ITU-R English is often not common, idiomatic American English, so your priorities may differ if you need to follow European English (or if you prefer old-fashioned usage, as in the base-ball game to be played to-day). -- Doug Ewell, CC, ALB | Lakewood, CO, US | ewellic.org